In a remarkable chapter on the Roman Campagna Sir Archibald Geikie has given the facts relating to the geological formation of those hills, which were to become later the cradle of the Roman civilisation, when the volcanic platform of the Campagna, no longer increased by fresh eruptions, was carved by subaërial agencies into the topography which it presents to‑day. Among such agencies, which were both chemical and biological, may be mentioned those which prepared the vegetable soil and clothed it with oaks and beeches on the hills, with laurels and myrtles along the sea-coast, and with reeds and equiseta on the banks of the river. Then came Man, who may have watched the last gigantic natural fireworks of the Alban volcanoes from Mount Soracte, which had by that time ceased to be an island.

As the President of the Royal Society has pointed out, the Capitoline, Palatine, Aventine and Caelian hills have survived owing to their being made of a more obdurate stone than the granular tufa of the Campagna. The Tiber, or that mass of water which later became the Tiber, had excavated the volcanic deposits of the Campagna, and had left these hills behind. Then man helped the Tiber to excavate caverns in the hills, and he piled up, as defensive walls, those blocks of tufa which had been cut away from their slopes. And a race of warriors grew there which eventually conquered the western world and brought back marbles and porphyries from afar, by means of which the slopes of the Roman hills were raised into platforms supporting temples and shrines, glittering like crystal and shining with gold, crimson and blue. One tall slender pillar arose, carved like oriental ivory and crowned with the statue of a great and just emperor, from the top of which one could look
p244around and understand how the levels of both the hills and valleys had been raised by the hand of man and had been covered by him with such majestic works.

The most important of the Roman hills is the Palatine: it dominates the valley of the Forum, and contains the ruins of the palace built by the architect Rabirius, about A.D. 91, for the last emperor of the Flavian dynasty, and my researches have for some time been confined to this area.

Archaeological strata seem to me to be a continuation of those with which geology deals, and if archaeology is to become a science, we must apply to it those same analytical methods which have enabled us to reconstruct the history of the earth during the pre-human period. I believe it is, above all, necessary to know the original natural conditions of the site on which a civilisation attained its full development, as these conditions must ever, in a certain measure, determine the distribution and the grouping of those buildings, which later became the monuments of the civilisation itself.

It has been proved that the valley between the Capitol and Quirinal was not excavated by man, but had been furrowed by the prehistoric Tiber; and as a natural consequence the inscription on the column of Trajan must have borne a meaning different from that attributed to it by tradition.2 So, in beginning the exploration of the imperial palace on the Palatine, I thought it was necessary to ascertain at the outset whether it occupied the site of a valley, the so‑called intermontium, or whether, as I supposed, it occupied the summit of the original hill, a far more conspicuous and noble site for such an important residence. The preliminary researches proved the latter view to be correct. Only a few feet under the atrium, the central court of the palace, I reached the primitive archaeological layers, resting upon the top of the clay which covered the volcanic leucitic tufa nucleus of the Palatine, and of the other Roman hills.

Having thus proved that the imperial palace occupied the top of a hill, not the bottom of a valley, I came to the conclusion that the earlier imperial palaces, and their first prototype, the house of Tiberius, must have occupied the same site.

The late republican houses, some of which have been described to us as being the richest and most important in Rome, must have enjoyed a view of the distant Alban hills, and of the valley of the Forum from the slopes of the hill itself. In later times these houses were levelled down to make place for the successive rebuildings of
p245the imperial residence, as it grew larger and larger. In the days of Domitian the imperial palace seems to have been a colossal domicile, that is to say, the ordinary Roman house, multiplied by six: just as the statue raised by Domitian himself, in the centre of the Forum, had the same colossal proportions.

I hoped, as I still hope, that it would be possible, by discovering some of the houses of the republican period which were buried under the palace, that we should be in a position to study the biography, and to analyse the evolution, of the structure of the houses themselves, in order to find out their primitive form and shape, and eventually, perhaps, to reach those elementary prototypes of the Roman residences, the huts of the primitive Latin inhabitants of the hill sacred to Pales, the shepherd goddess. It is of great importance to determine the site, the shape, and grouping of such primitive Latin dwellings on the Palatine, because the shape of the huts themselves may give some clue to the origin of the progenitors of the Romans.

The Romulian people, who founded Rome, were most probably shepherds, just issuing from nomadism, while the Sabines, who occupied the Capitoline hill, originally the pagus Saturnius, had already by this time attained to the agricultural stage of a people who had ceased to be nomadic.

The shrine of Vesta at the foot of the Palatine was round, while the shrines on the Capitoline and the temple of Saturn were rectangular. Even to this day the huts of the shepherds in the Roman Campagna are round, and the cottages of the peasants are rectangular in shape. If we follow the tradition preserved by Livy, a temple was dedicated to Jupiter Stator by Romulus, not in order to stop the flight of his Latin soldiers, but in order to ratify an agreement with the Sabines never to leave the place, renouncing thereby all the advantages of nomadism. The shrine of the Lares Publici which I discovered close to the foundations of the old temple of Jupiter Stator, opposite the arch of Titus and possibly the one established there, according to tradition, by Tatius, the king of the Sabines, is rectangular in shape.

Connected with this unwilling renunciation of nomadism, there may be some hidden meaning in the peculiar structure of the Pons Sublicius, the oldest bridge over the Tiber, which did not admit of any nails being driven into its wooden structure, as was the case with the curia of Cyzicus.

Geological formations are differentiated by their composition, texture, and by the relics of organisms found in them; and geological science has proceeded so far that it is possible to say beforehand what fossil remains will be found in a given formation, if the stratigraphical position of that formation shall have been correctly
p246determined. In the case of archaeological accumulations, some of which have remained unknown till now, it is absolutely necessary, if we are to raise archaeology to the level of a science, to be very careful to study the materials and the structures in their definitely ascertained chronological order.

This method of analysis, by which I was enabled to attain scientific accuracy in the exploration of the Forum, I have applied to investigation of the Palatine: I began my explorations on that hill in the area of the private basilica (fig. 40, A) on the right-hand side of the entrance to the palace, adjacent to the vestibule or throne-room (fig. 40, B) of Domitian.

The large crevices, caused by earthquakes, which split the whole of the Palatine hill, had also extended through the wall, close by one of the arches in the wall of the basilica: I knew that these arches indicated that there was something hollow underneath. I searched there and found a staircase leading down to a piscina of the time of Nero, of which five large compartments still remain, carefully plastered with opus signinum, which, however, is much decomposed by sodium chloride.

We are told by Suetonius that Nero caused sea-water to be brought from the sea to the Palatine, and sulphurous water from Tivoli. This latter was evidently meant to be used for bathing, but the sea-water was for the purpose of keeping fish. It is well-known that the Romans did not care for sea-baths, for they carried fresh water to their villas on the sea-coast. They had as much horror of the sea as they had of high mountains. Nero himself, in order to avoid a sea-voyage, excavated a wide canal to enable him to travel inland from the Tiber to the great arsenal of Misenum on the bay of Naples. We know of this work, because the excavation of the wide trench, capable of carrying two galleys abreast, caused the destruction of the vines from which the celebrated Caecuban wine was made.

The chambers of the piscina, communicating through arched doorways, remind one of what Varro says of the Roman fish-tanks or piscinae; he compares them to the palette of a painter, which is used to keep the colours separate. So in the piscinae the fish of different varieties were divided, the smaller from the larger, one kind from another, by means of nets. A careful study of the remains of the vast piscinae, which are to be seen along the sea-coast from Ansidonia to Puteoli, would perhaps make it possible to learn much more about the very ancient art of preserving and propagating fish. The Romans had special ships in which the young fish were conveyed in large quantities from the Aegean sea, and distributed for breeding purposes along the coast of Campania. Fresh-water fish were for the use of the plebeians: but the piscinae for the
p247salt-water fish were luxurious and costly appendages of the Roman patrician villas. Lucullus himself grew so fond of the fish that he was breeding that he did not care to eat any of them, but sent to the market for the fish for his table, and also bought there small fish to feed the large ones in his piscinae.

I cannot stop to go into further details on this subject, as I have to bring before your notice an older structure which is close to the Palatine piscina. It is one of the houses of the last years of the republic. The house is a most important one, because the central hall, cut through by the cylindrical substructures of the Neronian piscina, is decorated with fresco-paintings, important from both the artistic and the historical point of view, since they reveal the importation of symbols and of ornaments from Egypt and Asia Minor. These paintings are also technically important inasmuch as they indicate new pigments, which the invasion of Egypt introduced to the Romans, and which they adopted in their frescoes.

The early Greek paintings were based on four colours: white, black, red, and yellow. These colours could either have been got by the early Romans from materials obtainable from the mineral deposits in central Italy, or from burning pine-resin. But the pictures in the house which was cut through by the piscina, reveal to us a most magnificent and gorgeous polychrome entirely unknown to the primitive Romans, its effect being especially due to the lavish use of coeruleum, which is a light blue silicate of copper imported from Alexandria, a colour so much admired that in the days of Vitruvius cheap imitations of it were the fashion. The mixture of this blue with the best yellow ochre produced various tones of green. The red panels are of the most brilliant vermilion, which was procured from Monte Amiata. Some of the floral decorations are painted in a brilliant purple colour, obtained from the murex.

In the construction of this late republican house, again, a still more ancient house has been cut through, of which the staircase, in opus incertum, is still preserved. Under this staircase runs one corridor of the favissae, a mysterious system of hiding-places, stores, or treasure-rooms, which runs under the whole extent of the Palatine.

The exploration of the republican houses, under the basilica of Domitian, has supplied the first important data concerning the geological structure of the hill. It has shown that the houses themselves were built on a level surface which was obtained on the eastern slope of the hill by removing a thick layer of clay from the top of the horizontal surface of the underlying tufa rock. In order to carry out these researches on a larger scale, I began to explore the adjoining vestibule of the palace (fig. 40, B): a magnificent hall 120 feet wide, where Heraclius was crowned as the last emperor. Here, next the principal entrance, I was able to determine the chronological
p248succession of the imperial palaces. I saw how the substructures in silex-concrete of the palace of Domitian had cut through the substructures in travertine-concrete of a previous palace, probably that of Nero, which, in its turn, had cut through the older concrete substructures, containing late republican terracottas and broken tiles, and belonging to a still older palace, probably that of Caligula.

All these foundations of the three imperial palaces, of which we now know the chronological order, met in a certain spot, and there cut through the threshold and vestibule of another house of the late republican period, originally belonging to a patrician family such as that of Catiline. The threshold and the pavement are in slabs of the most beautiful and precious African red breccia separated by slabs of green-veined cipolline marble from the island of Euboea. The house shows an orientation quite different from that of the later palaces; and as its direction was towards the imperial lararium, I extended my researches there, and discovered the atrium, and the lateral rooms or cubicula, paved with marble slabs which covered mosaic floors belonging to an earlier period. These mosaics are not composed of fragments of marble but of pebbles from the Umbrian confluents of the Tiber, red, yellow, green, black and white limestones, grouped so as to produce a polychromatic effect, which is not only beautiful in itself, but historically interesting as important evidence of that aspiration towards a kind of decoration, a taste which the Romans were able to satisfy to the utmost later on, when they came into contact with the eastern and African marbles.

The new owner of this house, towards the beginning of the Augustan era, covered the old mosaic pavements with slabs of marble, threw down fragments of architectural remains, stuccos, and the like, which filled up the basement rooms of the original ground-floor. These remains have been most valuable, for I have been able to study in them the whole architectural and pictorial decoration of the older house. The original ground-floor itself is decorated with stuccos and pictures of silicious pebbles displaying the wavy concentric layers of chalcedony and agate, while the architectural framework in which they are set shows the first attempt at parallel perspective. Under this ground-floor are layers containing the terracotta decorations of a still older republican house of the third century B.C.; also a row of grottoes, cut in the tufa, filled up with the remains of what appears to have been a yet older house, if we may judge from its terracottas, which are of the archaic period, and from the relics of the life of the family, who seem to have occupied the site somewhere between the sixth and fifth centuries B.C. Among these interesting relics we found indigenous pottery, some articles meant for cooking, some for the table,
p249Campanian ware, black Etruscan bucchero, and the most exquisite early Attic, with inscriptions in archaic Latin, Etruscan and Greek. These remains reveal the presence of different races, and indicate intercourse and communication about the time of the Gallic invasion of 390 B.C. Here we came upon the terracotta weights of the vertical looms of the earlier epoch, and also animal bones, which indicated the animals slaughtered for food. Some of the bones had been utilised to manufacture rings, styli, or dice. Even the remains of the domestic fire revealed to us information concerning the oaks that shaded the Palatine, and the neighbouring hills, and concerning the willows that grew in the marshy valleys between.

These various remains are documents which, in importance to the archaeologist, may be compared to the fossil forms of plants and animals in geological enquiries. They enable us to recognise the stage of development of the inhabitants of the Palatine in the early republican days; and they give us approximately the date at which the favissae below were filled up. But the date when these excavations were first made is still to be discovered.

The first row of favissae under the republican house has several rectangular and cylindrical shafts leading down to corridors and galleries. These shafts, which are in most cases placed only a few yards apart, seem to have served for ventilation purposes, and fire could be burnt at the bottom of any one of them, just as in the early Iberian mines in Spain. The corridors and the galleries at the bottom of the shafts lead to chambers carefully plastered, which were used as granaries or safe-deposits, and were well protected against damp. A large cylindrical shaft has been sunk through the first tier of favissae, and at a depth of 60 feet it cuts through another very extensive and complicated network of corridors and galleries, shaped like the Christian catacombs. Passing through the tufa, it reaches a layer of clay intermixed with layers of sand, and still continuing its descent may perhaps have led to a still deeper tier of corridors, which I have not yet been able to reach.

Similar favissae were found under the central part of the atrium, and under the house of Tiberius Claudius, which represents the actual prototype of the imperial palace. Their exploration is rendered very difficult, by reason of the great depth to which they reach; but as they may contain the solution of important problems concerning the origin of the Romans themselves, or of their predecessors on the Palatine, it is certainly worth while to surmount every difficulty in order to establish the date of the different layers in these troglodytic excavations, and to accumulate all the facts which can be obtained from them. In former days, such problems as are here presented were either avoided or got rid of by simple definitions.
p250As one who has investigated the origin of the Romans has said: "The charm of simplicity has proved as fatal in problems of history as in those of natural science: for the deeper we penetrate into the inwardness of things, the more complex do all the phenomena of nature appear, and in no department can this be affirmed with greater certainty than in all that appertains to Man."

The Palatine favissae were supposed to be quarries, but their complicated structure, and the way in which they were plastered, made us look at them more closely, and compare them with similar excavations which are to be found all along the Latin coast, as far as Nettuno. Now, as has been said, "it is difficult to see something that does not yet bear a name, for, as people are usually constituted, it is the name that first makes a thing visible to them." In the case of these mysterious excavations, I think we may fitly employ the obsolete word favissae, which was the archaic Latin name for similar excavations under the Capitoline hill.3

Research will doubtless one day reveal when the Palatine favissae were first excavated, who excavated them, and for what purpose. We may, perhaps, look on these subterranean chambers and galleries as the predecessors of the Christian catacombs, and make certain comparisons in regard to them, since the people who issued from the catacombs seem to have had many points of similarity with the indigenous Mediterranean race who had at first been subjected by the Latin Romans, and waited patiently, as plebeians, to re-emerge when the patrician families, being worn out, were withdrawn from circulation by Nature. These patricians left behind them, in the sunlight of the Palatine and of the other Roman hills, many noble buildings, together with other evidences of their civilising power. Their visible monuments would become an easy spoil to the older indigenous races which had survived through centuries, like the pellitory on ruined walls, as well as to the ignorant barbarians, who in later generations had to find out for themselves how great was the civilisation which they had trodden upon and destroyed. As the destruction went on systematically through the dark ages, the flames kindled by ignorance or fanaticism deprived humanity for several centuries of the knowledge of much that the noblest races of antiquity had already discovered in different branches of science.

Mechanics, one of the most important of these branches, has to do with my present researches on the Palatine. Years ago, under the central part of the Roman Forum, I found a group of twelve elevators, worked by capstans, and used for the gladiatorial shows of
p251Julius Caesar. I was convinced that more powerful and complicated mechanical appliances must have been employed on the Palatine, and that these must have been on a much larger scale, on account of the greater difference in level between the Circus Maximus, which we may look upon as the ground floor of the imperial residence, and the official part of the palace, about 120 feet above. It was obvious also that the still higher level of the terraces, to which the water from the Neronian aqueduct had to be specially pumped in order to supply the necessary amount for the fountains, bathrooms, and the irrigation of the hanging gardens, would demand a large amount of mechanical energy for raising water and for working the lift and elevators for the rapid transit of persons and goods.4 We have also to account for mechanical power of sufficient magnitude to work the hydraulic organs, and also to move the circular dining-room of Nero which revolved like an astronomical dome, with the sun.

In the western nymphaeum (fig. 40, D), adjoining Domitian's dining-hall (fig. 40, C), I came upon one of the vertical shafts, about 5 feet in section, sunk in a line parallel to the Circus Maximus, and I excavated it to the depth of 120 feet without reaching the bottom. These shafts may have served for vertical communications between the palace and the lower level of the circus. Under the nymphaeum itself I found the marble and porphyry pavement of one of the magnificent halls of the Neronian palace, and about 30 feet lower a crypt-like room 22 feet wide and 6 feet long, with a large water-tank on the top of the massive vault, and, at the bottom, the remains of what may possibly be the stone framework for the horizontal cylinders of an hydraulic transformer, equipped with cogged-wheels. Of the engines themselves I found the extremity of a bronze cylinder, worked in a lathe, with a wing projecting inside of the cylinder, so as to prevent its revolving independently of the bar. There seem to have been twenty cylinders, which would, of course, develop out of a moderate quantity of water several hundred thousand foot-pounds of energy, quite enough to meet all the needs required. We do not know from the texts that have come down to us how the energy itself, once accumulated, was transformed into velocity and carried to a distance, but there are Greek texts and illustrations in the British Museum, and Arabic versions of Heron of Alexandria at Leyden, that will have to be studied, and some more facts may result from future explorations on the Palatine. I hope that the analysis of the traces left by the engine apparatus, and of the fragmentary texts of
p252the Greek and Roman engineers, will enable us to form an approximate idea of the state of knowledge in applied mechanics attained by our ancestors. In the meantime let us recognise that these men prepared the way for us in the realm of natural knowledge. The researches, which occupied for many centuries some of the noblest intellects of antiquity, led them to devise elementary engines and to discover fundamental principles, thus breaking ground for the still greater intellects who resumed the pursuit of experimental philosophy in the renaissance period, and whose successors have secured those triumphs in mechanics which are among the highest achievements of modern civilisation.

The Author's Notes:

1
This paper was read by Comm. Boni before the Royal Society, 12th June, 1913. It is printed here by his kindness and at the wish of the President of the Royal Society, Sir Archibald Geikie. The plan has been contributed by Mr. H. Stuart Jones.